1. Field of the Invention
The present invention relates to a power charging system, and more particularly, to a power charging system for portable electric devices.
2. Description of the Prior Art
In modern society, many people carry portable electric devices, such as a mobile phone, a PDA (personal digital assistant), a hand-held computer, a notebook computer, and so on. Many users carry two or more of these portable devices to access electrical data and interchange information with others. A charging system including a transformer and power cord designed for each portable electric device allows usage of these portable electric devices anytime and anywhere.
The convenience of portable electric devices becomes a disadvantage when users have to carry two or even more (depending on how many portable electric devices they carry) charging systems with them to charge their different portable electric devices. Please refer to FIG. 1. FIG. 1 is a schematic diagram illustrating a portable electric device 10A charging system according to prior art. The portable electric device 10A has a charging port 12A for inputting a DC (direct current) working voltage. Two corresponding transformers 16A and 18A are used to charge the portable electric device 10A. An AC (alternating current) power 20 is input via an input port 17A of the transformer 16A, altered by the transformer 16A to the working voltage of the portable electric device 10A, and output via an output port 14A of the transformer 16A. In a similar manner, a DC power 22 is input via an input port 19A of the transformer 18A, altered to the working voltage of the portable electric device 10A, and output via an output port 15A of the transformer 18A. Users can select the transformer 16A or 18A to charge the portable electric device 10A by connecting the input port of the transformer to a corresponding power source and connecting the output port of the transformer to the charging port 12A of the portable electric device 10A. In conclusion, an input power is first transformed into the specially designed working voltage of a portable device by a corresponding transformer, delivered from the output port of the transformer to the corresponding charging port of the portable electric device, and is finally used to charge the portable electric device.
According to a similar prior art, a portable electric device 10B, shown in FIG. 1, also has a specially designed charging port 12B for inputting its specially designed working voltage. The transformers 16B and 18B respectively have corresponding output ports 14B and 15B. An AC power 20 is input via an input port 17B of the transformer 16B, altered by the transformer 16B into the specially designed working voltage of the portable electric device 10B, and output to the charging port 12B via the output port 14B of the transformer 17B. Similarly, a DC power 22 is input via an input port 19B of the transformer 18B, altered to the specially designed working voltage of the portable electric device 10B, and output to the charging port 12B via the output port 15B of the transformer 18B.
Different portable electric devices have different specially designed working voltages. For example, the working voltage of modern portable electric devices varies from 3 volts to 12 volts. The charging port of each portable electric device also has a different shape and structure. A prior art portable electric device is equipped with its own specially designed transformer. These special transformers convert an input power via their input ports into the specially designed working voltage of the corresponding portable electric device. The output ports of these transformers must match the specially designed charging port of the portable electric device. Thus, when users carry two (or even more) portable electric devices, they have to carry corresponding specially designed transformers to charge their portable electric devices.
According to the prior art shown in FIG. 1, although the transformers 16A and 16B both can transform the AC power 20 to DC power, the transformed voltages that are output from each transformer are still the two specially designed and often different working voltages of the portable electric devices 10A and 10B. The output ports 14A and 14B of the transformers 16A and 16B also have different shapes. These two reasons make the specially designed transformer 16A of the portable electric device 10A incompatible with the portable electric device 10B. Likewise, the specially designed transformer 16B of the portable electric device 10B cannot charge the portable electric device 10A.
If users plan to charge a portable electric device with two different kinds of power sources, they have to carry at least two different specially designed transformers for each portable electric device to transform different power sources into the specially designed working voltage of the portable electric device. As shown in FIG. 1, users have to carry the two specially designed transformers 16A and 18A with them to charge the portable electric device 10A from two different power sources, the DC power 22 and the AC power 20.
A disadvantage of prior art is that users have to carry each specially designed transformer for each portable electric device to charge the portable electric device. It is obviously quite inconvenient for users to carry every possible charging combination for every portable electric device that they carry. Moreover, the weight and the volume of the transformers 16A or 16B, used in transforming AC power to DC power, is hard to further reduce. Additionally, it is also difficult to store power cords (power cords 21A and 23A of the transformers 16A and 18A) because of their lengths. Any portable electric device needs to be equipped with every kind of specially designed transformer to charge from different power sources, increasing the cost of portable electric devices and restricting the development of the information industry.